Si–N–O Films Synthesized by Plasma Immersion Ion Implantation and Deposition (PIII&D) for Blood-Contacting Biomedical Applications

Silicon-Oxynitride (Si–N–O) films were fabricated on silicon wafers by silicon cathodic arc combined with plasma immersion ion implantation and deposition. The blood compatibility of the films was assessed by platelet-adhesion test and fibrinogen conformational change measurements to evaluate the viability of the materials in biomedical engineering. Significantly, a better platelet-adhesion behavior, as manifested by a smaller number and weaker aggregation as well as pseudopodium, was observed on the Si–N–O samples compared to the low-temperature isotropic pyrolytic carbon, which is the most common material used in blood-contacting biomedical devices such as artificial heart valves. Enzyme-linked-immunoassay measurements that disclose fibrinogen conformational changes show results that are consistent with the platelets' behavior, which is believed to be involved in the activation process. The good blood compatibility of the films can be attributed to the high hydrophilicity and surface free energy arising from the Si–N, Si–N–O, and Si–O bonding states. The interfacial reactions between fibrinogen, platelets, and material surface are discussed from the perspective of thermodynamics. The promising blood compatibility of the Si–N–O films is of both scientific and commercial interests in biomedical engineering.